Gas separating and purifying method and its apparatus

ABSTRACT

The gas separation and purification process can recover efficiently a valuable gas such as krypton and xenon to be used as an atmospheric gas in a semiconductor manufacturing equipment etc. by means of PSA process. In the process for separating a valuable gas in the form of purified product from a mixed gas, used as a raw gas, containing the valuable gas by means of pressure swing adsorption process, the valuable gas is separated and purified by using as the pressure swing adsorption process a combination of equilibrium pressure swing adsorption process for separating gas components based on the difference in equilibrium adsorption and rate-dependent pressure swing adsorption process for separating the gas components based on the difference in adsorption rates.

TECHNICAL FIELD

[0001] The present invention relates to a gas separation andpurification process and an apparatus therefor, more specifically to aprocess and an apparatus for recovering a valuable gas in the form ofpurified product, and particularly to a gas separation and purificationprocess and an apparatus therefor, which can be most suitably used forrecovering and recycling valuable noble gases such as krypton and xenonto be used as atmospheric gases in semiconductor manufacturing equipmentand the like.

BACKGROUND ART

[0002] In a process for manufacturing semiconductor products such assemiconductor integrated circuits, liquid crystal panels, solar panelsand magnetic discs, there are used a wide variety of devices whichgenerate plasma in a noble gas atmosphere to carry out various kinds oftreatments for semiconductor products by the plasma thus generated, forexample, sputtering machines, plasma CVD reactors, reactive ion etchingmachines, etc.

[0003] Such processing devices are operated as follows: When substratesand the like to be treated are fed into a processing chamber, a nitrogengas atmosphere is formed in the processing chamber, and when a plasmatreatment is carried out, a noble gas is charged singly or optionallytogether with a gas which promotes the reaction to the chamber togenerate plasma by high-frequency discharge and carry out treatment ofthe substrates therewith. Subsequently, the chamber is purged bycharging nitrogen gas thereto, and the substrates are taken outtherefrom. As the gas for promoting the reaction in a treatment, forexample, in a plasma oxidation treatment, a certain quantity of oxygenis added.

[0004] While argon has predominantly been used as the noble gas to beemployed in such treatments, krypton and xenon having low ionizationpotentials are coming to the fore for more sophisticated applications.

[0005] Krypton and xenon are extremely expensive, since they are presentin air at very low ratios and require intricate separation processes, sothat the processes employing such gases are appreciated economically,only on the premise that used gases are recovered, purified andrecycled.

[0006] A mixed gas containing a noble gas to be separated and purifiedconsists mainly of a noble gas and nitrogen. In a plasma oxidationtreatment, such a mixed gas containing additionally a certain quantityof oxygen is used. Meanwhile, in a plasma CVD treatment and a reactiveion etching treatment, a metal hydrogen compound gas and a halogenatedcarbon gas are additionally used respectively. Further, moisture, carbonmonoxide, carbon dioxide, hydrogen, hydrocarbons, etc. are occasionallycontained as trace impurities.

[0007] Xenon is also drawing attention for its application as ananesthetic gas in the form of mixture with a predetermined amount ofoxygen (usually ca. 30%). The mixed gas to be subjected to theseparation and purification treatment is a patient's exhalationcontaining, for example, oxygen, nitrogen, carbon dioxide and moisturein addition to xenon. In this case, it is necessary to remove nitrogen,carbon dioxide, etc. from the mixed gas in order to recycle xenon.

[0008] Referring to the prior art to recover a specific component from amixed gas by the pressure swing adsorption (PSA) process and purifyingit, it is described extensively, for example, in a literature “PressureSwing Adsorption, 1994 VCH Publishers Inc., collaborated by D. M.Ruthven, S. Farooq and K. S. Knaebel”, Chapter 6.

[0009] Paragraph 6.5 of the literature explains a four-column PSAprocess for recovering hydrogen from various kinds of mixed gases andpurifying it. This hydrogen PSA process utilizes the nature of hydrogenthat it is extremely difficult to adsorb compared with other componentsof the mixed gas. Table 6.2 in the above literature shows testconditions and performance data of the four-column hydrogen PSApurification system. It is disclosed in Table 6.2 that if a high product(hydrogen) concentration of 99.9% or more is to be obtained in theconventional hydrogen PSA process, the rate of hydrogen recovery reducesto less than 80%.

[0010] Paragraph 6.6 of the above literature also explains a four-columnPSA process for recovering carbon dioxide gas from a combustion wastegas and purifying it. Table 6.4 in the literature shows performance dataof the PSA process for recovering carbon dioxide gas from a combustionwaste gas and purifying it. It is disclosed in Table 6.4 that even ifthe product had a relatively low concentration of about 99%, therecovery rate of carbon dioxide gas was at most about 72%.

[0011] Paragraph 6.7 of the above literature also explains a PSA processfor recovering methane from a gas occurring in dumpsite. It is disclosedin Paragraph 6.7 that when a recovery rate of 90% or higher is to beobtained by the conventional methane recovering PSA process, the producthad a methane concentration of 89%.

[0012] Meanwhile, Japanese Unexamined Patent Publication No. H6-182133(182133/94) discloses a process and an apparatus for recovering andpurifying a noble gas in a high yield. This invention relates torecovery and purification of helium, and helium is recovered while anoff-gas from the PSA process having been conventionally treated as awaste gas is recycled to be admixed to a raw gas, thus achieving highyield. However, the mixed raw gas is treated batchwise in this inventionand cannot be treated continuously.

[0013] Japanese Unexamined Patent Publication No. H10-273307 (273307/98)discloses as follows: “The chamber is purged with a purge gas to form agaseous outflow containing a noble gas and the purge gas, and theoutflow is recovered from the chamber for recycling. The purge gas ispreferably selected from hydrogen, steam, ammonia, carbon dioxide,carbon monoxide, oxygen and hydrocarbons having 2 to 6 carbon atoms. Anoble gas flow is preferably separated from the outflow by means ofmembrane separation, condensation, adsorption, absorption,crystallization or by a combination thereof.”

[0014] Further, Japanese Unexamined Patent Publication No. H11-157814(157814/99) discloses a process relating to switching between anoperation of introducing a noble gas-containing off-gas discharged froma plant where the noble gas is used to a recovery system and anoperation of discharging it therefrom. However, this invention merelydiscloses as follows: “While adsorption, membrane separation and thelike can be employed, a getter type purification apparatus employing ametal such as titanium, vanadium, zirconium and nickel or an alloythereof is suitably used.”

[0015] Japanese Unexamined Patent Publication No 2000-171589 discloses aprocess for recovering krypton/xenon using natural zeolite as a processfor recovering a radioactive noble gas. Although this inventiondiscloses adsorption of the noble gas contained in helium gas, there isno disclosure of desorption, recovery nor recycling thereof.

[0016] Japanese Unexamined Patent Publication No. 2000-26319 discloses aprocess for recovering lower hydrocarbons from an off-gas from apolyolefin manufacturing plant by means of PSA process. This inventionis directed to carrying out a recycling operation of mixing a purgeoff-gas to a raw gas so as to obtain a high recovery rate. However,according to embodiments of the invention, the recovery rate was about90% when the lower hydrocarbon concentration was 99.9%, and 10% of lowerhydrocarbons remained unrecovered.

[0017] As described heretofore, there has so far been neither processnor apparatus for recovering a specific component in a mixed gas by aPSA process continuously at a high purity and in a high recovery rate of95to 99% or more. Further, there are a very few published adsorptiondata on krypton and xenon. For example, Journal of Colloid and InterfaceScience, Vol. 29, No. 1, January 1969 describes adsorption data ofkrypton onto activated carbon and zeolite 5A at 25° C. According to thedata, it can be understood that activated carbon adsorbent adsorbs alarge amount of krypton over zeolite 5A. A process for recovering aneasily adsorbable component in the form of high-purity product isdisclosed, for example, in Japanese Unexamined Patent Publication No.H3-12212 (12212/91), describing a process for separating and recoveringnitrogen from air through three major steps ofadsorption-cleaning-desorption.

[0018] In a consideration based on the adsorption data on krypton asdescribed above, the activated carbon adsorbent has a sufficiently largeamount of krypton adsorption compared with the adsorption of nitrogen asan impurity component, so that the process disclosed in JapaneseUnexamined Patent Publication No. H3-12212 (12212/91) is deemed to beapplicable. However, in the process ibid., since there is used a largeamount of cleaning gas for obtaining a high-purity product, no highrecovery rate can be expected.

[0019] That is, it has been difficult in the prior art to enhancesufficiently economical efficiency in the system handling a noble gassuch as krypton and xenon. Particularly, none of the prior arttechniques incorporated herein was successful in recovering a valuablenoble gas by separation and purification from a mixed gas having beenrecovered by purging a chamber of a semiconductor manufacturingequipment with a nitrogen gas or by suction with a vacuum pump andcontaining the noble gas such as krypton and xenon like in the case asdescribed above, in an amount of about 25 to 75%. Thus, a noveltechnology has been awaited to be exploited.

[0020] As described above, in the conventional semiconductormanufacturing equipment and the like, once a valuable gas such askrypton or xenon is used as an atmospheric gas, it is released to theoutside, so that the cost of atmospheric gas notably increases,disadvantageously. Besides, there is a problem that it has beendifficult to recover the valuable noble gas from the chamber of thesemiconductor manufacturing equipment continuously by means of PSAprocess at a high purity and in a high recovery rate of 95% or more, andit has been far more difficult technologically to give a higher recoveryrate of 99% or more.

[0021] Therefore, the present invention is directed to providing a gasseparation and purification process and an apparatus therefor, which canrecover a valuable gas and purifying it efficiently by means of PSAprocess using as a raw gas a mixed gas containing a valuable gas such askrypton and xenon to be used as an atmospheric gas in semiconductormanufacturing equipment and the like.

DISCLOSURE OF THE INVENTION

[0022] In the gas separation and purification process according to thepresent invention, a valuable gas is separated in the form of purifiedproduct from a mixed gas, used as a raw gas, containing the valuable gasby means of pressure swing adsorption process, wherein the pressureswing adsorption process contains a combination of equilibrium pressureswing adsorption process for separating gas components based on thedifference in the amounts of adsorbed gases at equilibrium, andrate-dependent pressure swing process for separating the gas componentsbased on the difference in adsorption rates.

[0023] In the gas separation and purification process according to thepresent invention, the raw gas is separated into an easily adsorbablecomponent and a hardly adsorbable component by the equilibrium pressureswing adsorption process to release the hardly adsorbable component inthe equilibrium pressure swing adsorption process as an off-gas, whereasthe easily adsorbable component in the equilibrium pressure swingadsorption process is separated into an easily adsorbable component anda hardly adsorbable component by the rate-dependent pressure swingadsorption process to collect the hardly adsorbable component in therate-dependent pressure swing adsorption process as a product gas.Particularly, the easily adsorbable component in the rate-dependentpressure swing adsorption process is circulated to the equilibriumpressure swing adsorption process to be subjected to re-separationthere.

[0024] Further, the raw gas is separated into an easily adsorbablecomponent and a hardly adsorbable component by the rate-dependentpressure swing adsorption process to collect the hardly adsorbablecomponent in the rate-dependent pressure swing adsorption process as aproduct gas, whereas the easily adsorbable component in therate-dependent pressure swing adsorption process is separated into aneasily adsorbable component and a hardly adsorbable component by theequilibrium pressure swing adsorption process to release the hardlyadsorbable component in the equilibrium pressure swing adsorptionprocess as an off-gas. Particularly, the easily adsorbable component inthe equilibrium pressure swing adsorption process is circulated to therate-dependent pressure swing adsorption process to be subjected tore-separation there.

[0025] Further, the raw gas is separated into an easily adsorbablecomponent and a hardly adsorbable component by the rate-dependentpressure swing adsorption process to release the easily adsorbablecomponent in the rate-dependent pressure swing adsorption process as anoff-gas, whereas the hardly adsorbable component in the rate-dependentpressure swing adsorption process is separated into an easily adsorbablecomponent and a hardly adsorbable component by the equilibrium pressureswing adsorption process to collect the easily adsorbable component inthe equilibrium pressure swing adsorption process as a product gas.Particularly, the hardly adsorbable component in the equilibriumpressure swing adsorption process is circulated to the rate-dependentpressure swing adsorption process to be subjected to re-separationthere.

[0026] Further, the raw gas is partly separated into an easilyadsorbable component and a hardly adsorbable component by theequilibrium pressure swing adsorption process to release the hardlyadsorbable component in the equilibrium pressure swing adsorptionprocess as an off-gas, and the easily adsorbable component in theequilibrium pressure swing adsorption process is admixed with the rawgas; whereas the rest of the raw gas is separated into an easilyadsorbable component and a hardly adsorbable component by therate-dependent pressure swing adsorption process to collect the hardlyadsorbable component in the rate-dependent pressure swing adsorptionprocess as a product gas, and the easily adsorbable component in therate-dependent pressure swing adsorption process is admixed with the rawgas. Particularly, the raw gas is supplied to the equilibrium pressureswing adsorption process and the rate-dependent pressure swingadsorption process after pressurization, and the easily adsorbablecomponent in the equilibrium pressure swing adsorption process and theeasily adsorbable component in the rate-dependent pressure swingadsorption process are admixed with the raw gas before pressurization.

[0027] In a gas separation and purification apparatus according to thepresent invention, a valuable gas is separated in the form of purifiedproduct from a mixed gas, used as a raw gas, containing the valuable gasby a pressure swing adsorption unit, wherein the pressure swingadsorption unit contains an equilibrium pressure swing adsorption unit,which separates gas components based on the difference in equilibriumadsorption, and a rate-dependent pressure swing adsorption unit, whichseparates the gas components based on the difference in adsorptionrates.

[0028] Further, in the gas separation and purification apparatusaccording to the present invention, the equilibrium pressure swingadsorption unit is connected in series with the rate-dependent pressureswing adsorption unit such that the former unit is located on theupstream side and the latter unit is located on the downstream side; theupstream equilibrium pressure swing adsorption unit is provided with apassage for extracting a hardly adsorbable component in the equilibriumpressure swing adsorption unit as an off-gas and a passage forintroducing an easily adsorbable component in the equilibrium pressureswing adsorption unit to the downstream rate-dependent pressure swingadsorption unit; whereas the downstream rate-dependent pressure swingadsorption unit is provided with a passage for extracting a hardlyadsorbable component in the rate-dependent pressure swing adsorptionunit as a product gas and a passage for circulating an easily adsorbablecomponent in the rate-dependent pressure swing adsorption unit to theraw gas supply side of the equilibrium pressure swing adsorption unit.

[0029] Further, the gas separation and purification apparatus is furtherprovided with a passage for diverting the raw gas and supplying it intothe equilibrium pressure swing adsorption unit and to the downstreamrate-dependent pressure swing adsorption unit; a passage for admixingthe easily adsorbable component in the equilibrium pressure swingadsorption unit with air as a raw gas to be supplied to therate-dependent pressure swing adsorption unit; and a passage foradmixing the easily adsorbable component in the rate-dependent pressureswing adsorption unit with the raw gas air to be supplied to theequilibrium pressure swing adsorption unit.

[0030] Further, the equilibrium pressure swing adsorption unit usesactivated carbon as an adsorbent. The rate-dependent pressure swingadsorption unit uses Na—A zeolite or carbon molecular sieve as anadsorbent. The valuable gas is at least one of krypton and xenon.

[0031] According to the present invention, since valuable gases such askrypton and xenon contained in a mixed gas to be discharged from asemiconductor manufacturing equipment and the like using such a valuablegas can be recovered at a high purity and in a high recovery rate, thecost of the atmospheric gas in the semiconductor manufacturing equipmentetc. can be reduced notably.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 is a schematic diagram showing the gas separation andpurification apparatus according to a first embodiment of the presentinvention;

[0033]FIG. 2 is a diagram showing adsorption isotherm of krypton, xenonand nitrogen adsorbed on activated carbon;

[0034]FIG. 3 is a diagram showing adsorption isotherm of krypton andnitrogen adsorbed on zeolite 4A;

[0035]FIG. 4 is a diagram showing adsorption rates of krypton andnitrogen onto zeolite 4A;

[0036]FIG. 5 is a schematic diagram showing the gas separation andpurification apparatus according to a second embodiment of the presentinvention;

[0037]FIG. 6 is a schematic diagram showing the gas separation andpurification apparatus according to a third embodiment of the presentinvention;

[0038]FIG. 7 is a schematic diagram showing the gas separation andpurification apparatus according to a fourth embodiment of the presentinvention;

[0039]FIG. 8 is a schematic diagram showing the gas separation andpurification apparatus according to a fifth embodiment of the presentinvention; and

[0040]FIG. 9 is a schematic diagram showing the gas separation andpurification apparatus according to a sixth embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0041]FIG. 1 is a schematic diagram showing the gas separation andpurification apparatus according to a first embodiment of the presentinvention.

[0042] The gas separation and purification apparatus, which is designedto recover krypton or xenon as a valuable gas and to separate it as apurified product, is provided with an equilibrium pressure swingadsorption unit 10 and a rate-dependent pressure swing adsorption unit20. The equilibrium pressure swing adsorption unit 10 separates gascomponents based on the difference in equilibrium adsorption, and therate-dependent pressure swing adsorption unit 20 separates the gascomponents based on the difference in adsorption rates.

[0043] The equilibrium pressure swing adsorption unit 10 has a pluralityof adsorption columns 11 a and 11 b packed with an adsorbent such asactivated carbon, for which krypton and xenon are easily adsorbablecomponents, while nitrogen is a hardly adsorbable component; acompressor 12 for compressing a raw gas to a predetermined adsorptionpressure; and a plurality of valves provided at predetermined positionsso as to switch the adsorption columns 11 a and 11 b between anadsorption step and a regeneration step interchangeably.

[0044] Meanwhile, the rate-dependent pressure swing adsorption unit 20has a plurality of adsorption columns 21 a and 21 b packed with anadsorbent such as Na—A zeolite or carbon molecular sieve, for whichkrypton and xenon are hardly adsorbable components, while nitrogen is aneasily adsorbable component; a compressor 22 for supplying a feed gas tothe unit 20; and valves provided at predetermined positions so as toswitch the adsorption columns 21 a and 21 b between the adsorption stepand the regeneration step interchangeably.

[0045] Provided that a mixed gas of krypton and nitrogen is used as araw gas and that activated carbon and Na—A zeolite are used as theadsorbent in the equilibrium pressure swing adsorption unit 10 and thatin the rate-dependent pressure swing adsorption unit 20 respectively,there will be described procedures of separating krypton and nitrogen inthe raw gas from each other to obtain krypton in the form of purifiedproduct. It should be understood here that, in these units, theadsorption columns 11 a and 21 a are initially performing the adsorptionstep.

[0046] First, in the equilibrium pressure swing adsorption unit 10, theraw gas is introduced through a raw gas introducing passage 31 and iscompressed to a predetermined pressure by the compressor 12. Thecompressed raw gas passes through an inlet valve 13 a and flows into theadsorption column 11 a. Since the activated carbon packed in theadsorption columns 11 a and 11 b adsorbs nitrogen (N₂) with difficultyrather than krypton (Kr) and xenon (Xe), as shown by the adsorptionisotherm (at a temperature of 298 K.) in FIG. 2, the activated carbonadsorbs preferentially the easily adsorbable component krypton in theraw gas flowed into the adsorption column 11 a, whereas the hardlyadsorbable component nitrogen is discharged from the outlet end of theadsorption column 11 a into a primary off-gas releasing passage 32through an outlet valve 14 a. In the meantime, the other adsorptioncolumn 11 b is performing the regeneration step, and the adsorbed gas isdischarged through a regeneration valve 15 b to flow into a suction side(primary side) passage 33 of the compressor 22 of the rate-dependentpressure swing adsorption unit 20.

[0047] Here, it is possible to perform, at the time of switching betweenthe adsorption step and the regeneration step, a pressure equalizingoperation using a pressure equalizing passage 17 having pressureequalizing valves 16 a and 16 b, and a purge regeneration operation tointroduce a purge gas from the outlet side of the column in theregeneration step, like in the conventional PSA process.

[0048] Before the adsorption of krypton onto the activated carbon in theadsorption column 11 a reaches the critical limit to let krypton flowout through the column outlet, the inlet valves 13 a and 13 b, theoutlet valves 14 a and 14 b, and the regeneration valves 15 a and 15 bare switched to switch the steps in the adsorption columns 11 a and 11 bsuch that the adsorption column 11 a and the adsorption column 11 bperform the regeneration step and the adsorption step, respectively.

[0049] In the regeneration step, since the krypton adsorbed on theactivated carbon is desorbed therefrom upon reduction of the internalpressure of the column, the gas to be extracted from the adsorptioncolumn into the passage 33 in the regeneration step is a concentratedkrypton gas (primary purified gas) . After this primary purified gas iscompressed to a predetermined pressure by the compressor 22, it flowsthrough an inlet valve 23 a into the adsorption column 21 a performingthe adsorption step. Here, the passage 33 may be provided with a buffertank for equalizing the concentration and flow rate of the primarypurified gas.

[0050] While Na—A zeolite, the so-called zeolite 4A, packed in theadsorption columns 21 a and 21 b adsorbs krypton (Kr) and nitrogen (N₂)in almost equal amounts, as shown by the adsorption isotherm of FIG. 3,it adsorbs krypton (Kr) and xenon (Xe) slowly compared with nitrogen(N₂), as shown by the results of adsorption rate measurement shown inFIG. 4 (adsorption rate of xenon is too low to appear on the graph ofFIG. 4). Thus, zeolite 4A adsorbs preferentially nitrogen as an easilyadsorbable component which is adsorbed quickly and easily among othercomponents of the primary purified gas flowed into the adsorption column21 a, whereas krypton is extracted from the outlet end of the adsorptioncolumn 21 a and flows through an outlet valve 24 a into a secondarypurified gas extracting passage 34 as a hardly adsorbable componentwhich is adsorbed slowly and hardly by zeolite 4A. The gas extracted tothe secondary purified gas extracting passage 34 is stored temporarilyas a product krypton in a product storage tank 35 and then suppliedthrough a product extracting passage 36 to a site where the product gasis used. The graduation along the axis of ordinate shown in FIG. 4indicates residual adsorbable quantity when the equilibrium adsorptionis 1 at a given temperature.

[0051] When the adsorption column 21 a is performing the adsorptionstep, the adsorption column 21 b is performing the regeneration step. Inthe regeneration step, a regeneration valve 25 b is opened to dischargethe gas in the adsorption column 21 b to a secondary off-gas extractingpassage 37. It is here again possible to perform, at the time ofswitching between the adsorption step and the regeneration step, thepressure equalizing operation using a pressure equalizing passage 27having pressure equalizing valves 26 a and 26 b, and a purgeregeneration operation to introduce a purge gas from the outlet side ofthe column in the regeneration step, like in the conventional PSAprocess.

[0052] Before the adsorption of nitrogen onto the zeolite 4A in theadsorption column 21 a reaches the critical limit to let nitrogen flowout through the column outlet, the inlet valves 23 a and 23 b, theoutlet valves 24 a and 24 b, and the regeneration valves 25 a and 25 bare switched to switch the steps in the adsorption columns 21 a and 21 bsuch that the adsorption column 21 a and the adsorption column 21 bperform the regeneration step and the adsorption step, respectively.

[0053] In the regeneration step, not only the nitrogen desorbed from thezeolite 4A is released but also the primary purified gas present in thecolumn flows out upon reduction of the internal pressure of the column,so that the secondary off-gas to be discharged in the regeneration stepof the rate-dependent pressure swing adsorption unit 20 contains asubstantial amount of krypton. Therefore, the secondary off-gasdischarged into the secondary off-gas extracting passage 37 is recycledto the primary side of the compressor 12 to be admixed to the raw gas,and the resulting mixed gas is subjected to re-separation in theequilibrium pressure swing adsorption unit 10. Thus, the kryptoncontained in the secondary off-gas can be recovered into the primarypurified gas.

[0054] In each of the pressure swing adsorption units 10 and 20, whilethe concentration of the easily adsorbable component contained in thehardly adsorbable component flowing out from the adsorption column inthe adsorption step tends to increase with time, the content of nitrogento be contained as an impurity in the product krypton collected finallyfrom the secondary purified gas extracting passage 34 can be controlledby adjusting the amount of the hardly adsorbable component to beextracted during a predetermined period of adsorption step, so that theperiod of adsorption step and the amount of hardly adsorbable componentto be extracted can be determined in view of purity required of theproduct krypton and of economical efficiency.

[0055]FIG. 5 is a schematic diagram showing the gas separation andpurification apparatus according to a second embodiment of the presentinvention. It should be noted here that in the following description thesame or like components as those in the first embodiment are affixedwith the same reference numbers respectively, and detailed descriptionsof them will be omitted.

[0056] The gas separation and purification apparatus shown in thisembodiment exemplifies a case where the apparatus has a combination ofthe equilibrium pressure swing adsorption unit 10 and the rate-dependentpressure swing adsorption unit 20 like in the first embodiment, and araw gas introducing passage 41 provided on the primary side passage 33of the compressor 22 of the rate-dependent pressure swing adsorptionunit 20. In other words, the equilibrium pressure swing adsorption unit10 and the rate-dependent pressure swing adsorption unit 20 are combinedwith each other such that the unit 20 locates on the upstream side andthe unit 10 locates on the downstream side.

[0057] The raw gas from the raw gas introducing passage 41 is compressedby the compressor 22 and then introduced to the rate-dependent pressureswing adsorption unit 20, where the hardly adsorbable component kryptonand the easily adsorbable component nitrogen are separated from eachother by the zeolite 4A packed in the adsorption column 21 a (21 b) ofthe unit 20. The hardly adsorbable component krypton is supplied fromthe purified gas extracting passage 34 a, and through the productstorage tank 35 and the product lead-out passage 36, to a site where theproduct gas is used.

[0058] The primary off-gas extracted from the rate-dependent pressureswing adsorption unit 20 to a primary off-gas extracting passage 37 a iscompressed by the compressor 12 and introduced to the equilibriumpressure swing adsorption unit 10, where the easily adsorbable componentkrypton and the hardly adsorbable component nitrogen contained in theprimary off-gas are separated from each other by the activated carbonpacked in the adsorption column 11 a (11 b) of the unit 10, and thehardly adsorbable component nitrogen is exhausted through the off-gasreleasing passage 32 a.

[0059] Meanwhile, the secondary purified gas extracted through theregeneration valve 15 a (15 b) in the regeneration step of theequilibrium pressure swing adsorption unit 10 passes through a passage37 b and flows into the primary side passage 33 of the compressor 22 tobe admixed to the raw gas introduced through the raw gas introducingpassage 41. The resulting mixed gas is then introduced to therate-dependent pressure swing adsorption unit 20 and is subjected tore-separation there.

[0060]FIG. 6 is a schematic diagram showing the gas separation andpurification apparatus according to a third embodiment of the presentinvention. The apparatus has a combination of the equilibrium pressureswing adsorption unit 10 and the rate-dependent pressure swingadsorption unit 20 like in the first embodiment, and a raw gasintroducing passage 51 which is diverged into a passage 52 and a passage53. One passage 52 is connected to the primary side of the compressor 12of the equilibrium pressure swing adsorption unit 10, and the otherpassage 53 is connected to the primary side of the compressor 22 of therate-dependent pressure swing adsorption unit 20.

[0061] More specifically, the raw gas partly flows through the passage52 and is combined with the secondary off-gas flowing through thesecondary off-gas extracting passage 37, and the resulting mixed gas iscompressed by the compressor 12 and is introduced into the equilibriumpressure swing adsorption unit 10, whereas the rest of the raw gaspasses through the passage 53 to be combined with the primary purifiedgas, i.e., the easily adsorbable component in the equilibrium pressureswing adsorption unit 10, flowing through the primary side passage 33 ofthe compressor 22. The resulting mixed gas is then compressed by thecompressor 22 and then introduced to the rate-dependent pressure swingadsorption unit 20. The easily adsorbable component in therate-dependent pressure swing adsorption unit 20 flows through thesecondary off-gas extracting passage 37 and is admixed with the raw gasof the passage 52 for recycling.

[0062]FIG. 7 is a schematic diagram showing the gas separation andpurification apparatus according to a fourth embodiment of the presentinvention. The apparatus has a combination of the equilibrium pressureswing adsorption unit 10 and the rate-dependent pressure swingadsorption unit 20. In this apparatus, a gas is designed to beintroduced from a single compressor 61 to both of these adsorption units10 and 20, and a buffer tank 62 is provided on the primary side of thecompressor 61. To the buffer tank 62 are connected a raw gas introducingpassage 63, a passage 64 (through which the gas extracted in theregeneration step in the equilibrium pressure swing adsorption unit 10flows) and a passage 65 (through which a gas extracted in theregeneration step in the rate-dependent pressure swing adsorption unit20 flows) so as to mix these gases, and the mixed gas is designed to bepressure-fed from the compressor 61.

[0063] More specifically, the raw gas flowed into the buffer tank 62from the raw gas introducing passage 63 is mixed with the gases flowedinto it through the passages 64 and 65, and the resulting mixed gas issucked into the compressor 61 and is introduced into the adsorptioncolumns performing the adsorption step in the adsorption units 10 and 20through a passage 66. Meanwhile, the gases extracted from the adsorptioncolumns performing the regeneration step in the adsorption units 10 and20 flow through the passages 64 and 65 respectively to be recycled tothe buffer tank 62, and the resulting mixed gas is subjected tore-separation. This constitution can reduce the number of compressors tobe installed.

[0064]FIG. 8 is a schematic diagram showing the gas separation andpurification apparatus according to a fifth embodiment of the presentinvention. This embodiment shows an example, where the apparatus has acombination of the equilibrium pressure swing adsorption unit 10 withthe rate-dependent pressure swing adsorption unit 20 such that the unit20 and the unit 10 are located on the upstream side (raw gas supplyside) and on the downstream side respectively, contrary to the firstembodiment, and the easily adsorbable component in the equilibriumpressure swing adsorption unit 10 is collected as a product.

[0065] In this embodiment, the raw gas containing a mixture of kryptonand nitrogen is introduced through a raw gas introducing passage 71, andkrypton which is a hardly adsorbable component for zeolite 4A in therate-dependent pressure swing adsorption unit 20 is extracted in theadsorption step through the outlet valve 24 a (24 b) into a primarypurified gas passage 38 and then introduced into the equilibriumpressure swing adsorption unit 10. Here, since the primary purified gasis extracted at a predetermined adsorption pressure in the adsorptionstep, the gas can be introduced as such into the equilibrium pressureswing adsorption unit 10 without compression by a compressor.

[0066] In the equilibrium pressure swing adsorption unit 10, kryptonwhich is an easily adsorbable component for activated carbon isextracted from the adsorption column in the regeneration step into asecondary purified gas extracting passage 39 through the regenerationvalve 15 a (15 b) and is supplied through the product storage tank 35and the product extracting passage 36 to a site where the product gas isused.

[0067] Meanwhile, the gas extracted from the adsorption columnperforming the adsorption step in the equilibrium pressure swingadsorption unit 10 is led through the outlet valve 14 a (14 b) into thesecondary off-gas extracting passage 37 and is recycled to the primaryside of the compressor 22 to be admixed to the raw gas, and theresulting mixed gas is subjected to re-separation in the rate-dependentpressure swing adsorption unit 20. Meanwhile, the gas (nitrogen)extracted from the adsorption column performing the regeneration step inthe rate-dependent pressure swing adsorption unit 20 through theregeneration valve 25 a (25 b) is released through the primary off-gasreleasing passage 32.

[0068] Here, the secondary off-gas to be recycled through the secondaryoff-gas extracting passage 37 to the rate-dependent pressure swingadsorption unit 20 may be introduced thereto after compression by acompressor (not shown) provided on the secondary off-gas extractingpassage 37. Further, the product extracting passage 36 may, asnecessary, be provided with a compressor for pressure-feeding krypton.

[0069] In the second to fifth embodiments, the pressure swing adsorptionunits 10 and 20 each perform separation of krypton and nitrogen fromeach other continuously by switching the adsorption columns 11 a and 11b (21 a and 21 b) between the adsorption step and the regeneration stepinterchangeably to achieve separation and purification of kryptoncontained in the raw gas like in the first embodiment.

[0070] It should be noted here that, while a mixed gas of krypton andnitrogen was given as an example of the simplest raw gas composition ineach of the foregoing embodiments, the mixed gas may contain xenon andnitrogen, and xenon can be separated and collected likewise. The mixedgas of xenon and nitrogen may additionally contain krypton. Further,valuable gases which can be separated and purified according to thepresent invention include those containing high-purity isotopes such as¹H₂, D_(2,) ³He, ¹³CO, C¹⁸O₂, C¹⁷O₂, ¹⁸O₂, ¹⁷O₂, H₂ ¹⁸O₂, H₂ ¹⁷O₂, D₂O,¹⁵N₂, ¹⁵N₂O, ¹⁵NO and ¹⁵NO₂.

[0071] Meanwhile, the gas to be released as the primary off-gas or gasesother than the valuable gas, such as oxygen, moisture, carbon monoxide,carbon dioxide, hydrogen and hydrocarbons can also be separated likewisefrom the valuable gas like in the case of nitrogen as described above.Further, the position where the raw gas is introduced may suitably beselected depending on the composition, flow rate, etc. of the mixed gasto be supplied as a raw gas. In addition, the constitution of eachpressure swing adsorption unit may suitably be selected, and there maybe employed a multi-column system having three or more adsorptioncolumns.

[0072]FIG. 9 is a schematic diagram of the gas separation andpurification apparatus according to a sixth embodiment of the presentinvention, showing an example where a pretreatment separation unit 80 isinstalled on the upstream side of the gas separation and purificationapparatus having a combination of the equilibrium pressure swingadsorption unit 10 and the rate-dependent pressure swing adsorption unit20.

[0073] This embodiment is suitable for treating a mixed gas (raw gas)containing relatively large amounts of moisture and carbon dioxide, forexample, in the case where xenon used as an anesthetic gas is separatedfrom a patient's exhalation in the form of purified product.

[0074] The pretreatment separation unit 80 has a pair of adsorptioncolumns 81 a and 81 b, a pair of inlet valves 82 a and 82 b, a pair ofoutlet valves 83 a and 83 b, a pair of regeneration gas inlet valves 84a and 84 b, and a pair of regeneration gas outlet valves 85 a and 85 b.An adsorbent such as zeolite, carbon molecular sieve and the like forremoving moisture and carbon dioxide is packed in the adsorption columns81 a and 81 b, and the moisture and carbon dioxide contained in the rawgas are designed to be separated by means of temperature swingadsorption process.

[0075] More specifically, the raw gas from the raw gas introducingpassage 31 is compressed by the compressor 12 and then introduced intothe pretreatment separation unit 80 where the moisture and carbondioxide are removed, and the resulting raw gas is introducedsuccessively to the equilibrium pressure swing adsorption unit 10 andthe rate-dependent pressure swing adsorption unit 20 of the gasseparation and purification apparatus and is extracted to the secondarypurified gas extracting passage 34. The gas extracted to the secondarypurified gas extracting passage 34 is stored temporarily as a productxenon in the product storage tank 35 and then supplied through theproduct extracting passage 36 to a site where the product gas is used.

[0076] By removing beforehand moisture, carbon dioxide and otherimpurity components in the pretreatment separation unit 80 as describedabove, the moisture and the like which are likely to be adsorbed byvarious kinds of adsorbents can be prevented from accumulating in thesystem of the gas separation and purification apparatus. Incidentally,the gas separation and purification apparatus to which the pretreatmentseparation unit 80 is installed may have a desired constitution, and,for example, any of those in the first to fifth embodiments can beemployed.

EXAMPLE 1

[0077] The gas separation and purification apparatus shown in FIG. 1 wasused to carry out a test for separating and purifying a noble gas. Inthe equilibrium pressure swing adsorption unit 10, each adsorptioncolumn having an inside diameter of 70 mm and a length of 1,000 mm waspacked with 1.7 kg of activated carbon as an adsorbent, and the unit 10was operated under the following conditions:

[0078] Half cycle time of equilibrium separation operation: 420 sec.;Pressure in the adsorption step: 604 kPa; and Pressure in theregeneration step: 102 kPa.

[0079] Meanwhile, in the rate-dependent pressure swing adsorption unit20, each adsorption column having an inside diameter of 70 mm and alength of 1,000 mm was packed with 2.6 kg of zeolite 4A as an adsorbent,and the unit 20 was operated under the following conditions:

[0080] Half cycle time of equilibrium separation operation: 300 sec.;Pressure in the adsorption step: 828 kPa; and Pressure in theregeneration step: 102 kPa.

[0081] A mixed gas of krypton (51.5%) and nitrogen (48.5%) wasintroduced as a raw gas to this gas separation and purificationapparatus at a flow rate of 2 L/min. (the flow rate [L/min.] is aconversion to a value as measured at 0° C. and at 1 atm.; the same shallapply hereinafter) Thus, a nitrogen gas having a concentration of 97%was released through the primary off-gas releasing passage 32 of theequilibrium pressure swing adsorption unit 10 at a flow rate of 1L/min., whereas a krypton gas having a concentration of 99.9% wascollected through the secondary purified gas extracting passage 34 at aflow rate of 1 L/min. Here, the secondary off-gas flowing through thesecondary off-gas extracting passage 37 had a krypton concentration of43% and a flow rate of about 4 L/min.

EXAMPLE 2

[0082] The gas separation and purification apparatus shown in FIG. 5 wasused to carry out a test for separating and purifying a noble gas. Inthe equilibrium pressure swing adsorption unit 10, each adsorptioncolumn was packed with 2.0 kg of activated carbon as an adsorbent.Meanwhile, in the rate-dependent pressure swing adsorption unit 20, eachadsorption column was packed with 5.0 kg of zeolite 4A as an adsorbent.

[0083] A mixed gas of krypton (30%) and nitrogen (70%) was introduced asa raw gas to this gas separation and purification apparatus at a flowrate of 2 L/min. Thus, a nitrogen gas having a concentration of 99.9%was released through the primary off-gas releasing passage 32 of theequilibrium pressure swing adsorption unit 10 at a flow rate of 1.4L/min., whereas a krypton gas having a concentration of 99.99% wascollected through the secondary purified gas extracting passage 34 at aflow rate of 0.6 L/min. Here, the secondary off-gas flowing through thesecondary off-gas extracting passage 37 had a krypton concentration of37% and a flow rate of about 9.4 L/min.

EXAMPLE 3

[0084] The gas separation and purification apparatus shown in FIG. 6 wasused to carry out a test for separating and purifying a noble gas. Inthe equilibrium pressure swing adsorption unit 10, each adsorptioncolumn was packed with 4.0 kg of activated carbon as an adsorbent.Meanwhile, in the rate-dependent pressure swing adsorption unit 20, eachadsorption column was packed with 4.0 kg of zeolite 4A as an adsorbent.

[0085] A mixed gas of krypton (70%) and nitrogen (30%) was introduced asa raw gas to this gas separation and purification apparatus at a flowrate of 2 L/min. Thus, a nitrogen gas having a concentration of 99.9%was released through the primary off-gas releasing passage 32 of theequilibrium pressure swing adsorption unit 10 at a flow rate of 0.6L/min., whereas a krypton gas having a concentration of 99.99% wascollected through the secondary purified gas extracting passage 34 at aflow rate of 1.4 L/min. Here, the secondary off-gas flowing through thesecondary off-gas extracting passage 37 had a krypton concentration of80% and a flow rate of about 6 L/min.

EXAMPLE 4

[0086] The gas separation and purification apparatus shown in FIG. 7 wasused to carry out a test for separating and purifying a noble gas. Inthe equilibrium pressure swing adsorption unit 10, each adsorptioncolumn was packed with 3.0 kg of activated carbon as an adsorbent.Meanwhile, in the rate-dependent pressure swing adsorption unit 20, eachadsorption column was packed with 4.0 kg of zeolite 4A as an adsorbent.

[0087] A mixed gas of krypton (50%) and nitrogen (50%) was introduced asa raw gas to this gas separation and purification apparatus at a flowrate of 2 L/min. Thus, a nitrogen gas having a concentration of 99.9%was released through the primary off-gas releasing passage 32 of theequilibrium pressure swing adsorption unit 10 at a flow rate of 1.0L/min., whereas a krypton gas having a concentration of 99.99% wascollected through the secondary purified gas extracting passage 34 at aflow rate of 1.0 L/min.

EXAMPLE 5

[0088] The gas separation and purification apparatus shown in FIG. 8 wasused to carry out a test for separating and purifying a noble gas. Inthe equilibrium pressure swing adsorption unit 10, each adsorptioncolumn was packed with 3.0 kg of activated carbon as an adsorbent.Meanwhile, in the rate-dependent pressure swing adsorption unit 20, eachadsorption column was packed with 4.0 kg of zeolite 4A as an adsorbent.

[0089] A mixed gas of krypton (50%) and nitrogen (50%) was introduced asa raw gas to this gas separation and purification apparatus at a flowrate of 2 L/min. Thus, a nitrogen gas having a concentration of 99.9%was released through the primary off-gas releasing passage 32 of theequilibrium pressure swing adsorption unit 10 at a flow rate of 1.0L/min., whereas a krypton gas having a concentration of 99.99% wascollected through the secondary purified gas extracting passage 34 at aflow rate of 1.0 L/min.

1. (deleted)
 2. (amended) In a gas separation and purification processfor separating a valuable gas in the form of purified product from amixed gas, used as a raw gas, containing the valuable gas by means ofpressure swing adsorption process, wherein the improvement whichcomprises: separating the raw gas into an easily adsorbable componentand a hardly adsorbable component by equilibrium pressure swingadsorption process to release the hardly adsorbable component as anoff-gas; and separating the easily adsorbable component into an easilyadsorbable component and a hardly adsorbable component by rate-dependentpressure swing adsorption process to collect the hardly adsorbablecomponent separated by the rate-dependent pressure swing adsorptionprocess as a product gas.
 3. The gas separation and purification processaccording to claim 2, wherein the easily adsorbable component separatedby the rate-dependent pressure swing adsorption process is circulated tothe equilibrium pressure swing adsorption process to be subjected tore-separation there.
 4. (deleted)
 5. (amended) In a gas separation andpurification process for separating a valuable gas in the form ofpurified product from a mixed gas, as a raw gas, containing the valuablegas by means of pressure swing adsorption process, wherein theimprovement which comprises: separating the raw gas into an easilyadsorbable component and a hardly adsorbable component by rate-dependentpressure swing adsorption process to collect the hardly adsorbablecomponent as a product gas; separating the easily adsorbable componentinto an easily adsorbable component and a hardly adsorbable component byequilibrium pressure swing adsorption process to release the hardlyadsorbable component separated by the equilibrium pressure swingadsorption process as an off-gas; and circulating the easily adsorbablecomponent separated by the equilibrium pressure swing adsorption processto the rate-dependent pressure swing adsorption process to be subjectedto re-separation there
 6. (deleted)
 7. (deleted)
 8. (amended) In a gasseparation and purification process for separating a valuable gas in theform of purified product from a mixed gas, used as a raw gas, containingthe valuable gas by means of pressure swing adsorption process, whereinthe improvement which comprises: separating the raw gas partly into aneasily adsorbable component and a hardly adsorbable component byequilibrium pressure swing adsorption process to release the hardlyadsorbable component as an off-gas and to admix the easily adsorbablecomponent with the raw gas; separating the rest of the raw gas into aneasily adsorbable component and a hardly adsorbable component byrate-dependent pressure swing adsorption process to collect the hardlyadsorbable component separated by the rate-dependent pressure swingadsorption process as a product gas; and admixing the easily adsorbablecomponent separated by the rate-dependent pressure swing adsorptionprocess with the raw gas.
 9. (amended) The gas separation andpurification process according to claim 8, wherein the part of and therest of the raw gas are subjected to separation by the equilibriumpressure swing adsorption process and also to separation by therate-dependent pressure swing adsorption process after pressurizationrespectively, and the easily adsorbable component separated by theequilibrium pressure swing adsorption process and the easily adsorbablecomponent separated by the rate-dependent pressure swing adsorptionprocess are admixed to the raw gas before pressurization.
 10. (deleted)11. (amended) A gas separation and purification apparatus for separatinga valuable gas in the form of purified product from a mixed gas, used asa raw gas, containing the valuable gas by a pressure swing adsorptionunit, wherein the pressure swing adsorption unit comprises a combinationof an equilibrium pressure swing adsorption unit and a rate-dependentpressure swing adsorption unit arranged in series such that the formerunit is located on the upstream side and the latter unit is located onthe downstream side; the equilibrium pressure swing adsorption unitbeing provided with a passage for extracting a hardly adsorbablecomponent separated by the equilibrium pressure swing adsorption unit asan off-gas and a passage for introducing an easily adsorbable componentseparated by the equilibrium pressure swing adsorption unit to therate-dependent pressure swing adsorption unit; whereas therate-dependent pressure swing adsorption unit being provided with apassage for extracting a hardly adsorbable component separated by therate-dependent pressure swing adsorption unit as a product gas. 12.(amended) A gas separation and purification apparatus for separating avaluable gas in the form of purified product from a mixed gas, used as araw gas, containing the valuable gas by a pressure swing adsorptionunit, the apparatus comprising: an equilibrium pressure swing adsorptionunit and a rate-dependent pressure swing adsorption unit; a passage fordiverting the raw gas and supplying it into the equilibrium pressureswing adsorption unit and to the rate-dependent pressure swingadsorption unit; a passage for admixing an easily adsorbable componentseparated by the equilibrium pressure swing adsorption unit with the rawgas air to be supplied to the rate-dependent pressure swing adsorptionunit; and a passage for admixing an easily adsorbable componentseparated by the rate-dependent pressure swing adsorption unit with theair as a raw gas to be supplied to the equilibrium pressure swingadsorption unit.
 13. (deleted)
 14. (deleted)
 15. (deleted)
 16. (added)The gas separation and purification apparatus according to claim 11,further comprising a passage for circulating an easily adsorbablecomponent separated by the rate-dependent pressure swing adsorption unitto the raw gas supply side of the equilibrium pressure swing adsorptionunit.
 17. (added) A gas separation and purification apparatus forseparating a valuable gas in the form of purified product from a mixedgas, used as a raw gas, containing the valuable gas by a pressure swingadsorption unit, wherein the pressure swing adsorption unit comprises acombination of a rate-dependent pressure swing adsorption unit and anequilibrium pressure swing adsorption unit arranged in series such thatthe former unit is located on the upstream side and the latter unit islocated on the downstream side; the rate-dependent pressure swingadsorption unit being provided with a passage for extracting a hardlyadsorbable component separated by the rate-dependent pressure swingadsorption unit as an off-gas and a passage for introducing an easilyadsorbable component separated by the rate-dependent pressure swingadsorption unit to the equilibrium pressure swing adsorption unit;whereas the equilibrium pressure swing adsorption unit being providedwith a passage for extracting a hardly adsorbable component separated bythe equilibrium pressure swing adsorption unit as a product gas and apassage for circulating an easily adsorbable component separated by theequilibrium pressure swing adsorption unit to a raw gas supply side ofthe rate-dependent pressure swing adsorption unit.
 18. (added) A gasseparation and purification apparatus for separating a valuable gas inthe form of purified product from a mixed gas, used as a raw gas,containing the valuable gas by a pressure swing adsorption unit, theapparatus comprising: an equilibrium pressure swing adsorption unit anda rate-dependent pressure swing adsorption unit; a compressor forsupplying a raw gas to both of the equilibrium pressure swing adsorptionunit and the rate-dependent pressure swing adsorption unit; and a buffertank provided on the primary side of the compressor; and a raw gasintroducing passage, a passage through which a gas extracted in aregeneration step of the equilibrium pressure swing adsorption unitflows and a passage through which a gas extracted in a regeneration stepof the rate-dependent pressure swing adsorption unit flows, all of whichbeing connected to the buffer tank so as to mix these gases; wherein theresulting mixed gas is designed to be pressure-fed from the compressorto both pressure swing adsorption units.
 19. (added) The gas separationand purification apparatus according to any one of claims 11, 12, 16, 17and 18, further comprising a pretreatment separation unit provided onthe upstream side of the apparatus; the pretreatment separation unitremoves beforehand moisture, carbon dioxide and other impuritycomponents contained in the raw gas.
 20. (added) The gas separation andpurification apparatus according to any one of claims 11, 12, 16, 17.and 18, wherein the equilibrium pressure swing adsorption unit usesactivated carbon as an adsorbent.
 21. (added) The gas separation andpurification apparatus according to any one of claims 11, 12, 16, 17 and18, wherein the rate-dependent pressure swing adsorption unit uses Na—Azeolite or carbon molecular sieve as an adsorbent.
 22. (added) The gasseparation and purification apparatus according to any of claims 11, 12,16, 17 and 18, wherein the valuable gas is at least one of krypton andxenon.
 23. (added) In a gas separation and purification process forseparating a valuable gas in the form of purified product from a mixedgas, used as a raw gas, containing the valuable gas by means of pressureswing adsorption process, wherein the improvement which comprises: usingas the pressure swing adsorption process two kinds of adsorptionprocesses (one is equilibrium pressure swing adsorption process and theother is rate-dependent pressure swing adsorption process); recoveringan easily adsorbable component separated by the equilibrium pressureswing adsorption process to a raw material supply side at the time ofregeneration desorption; recovering an easily adsorbable componentseparated by the rate-dependent pressure swing adsorption process to theraw material supply side at the time of regeneration desorption; andadmixing these recovered gases with the raw gas to pressure-feed theresulting mixed gas to an apparatus using these two pressure swingadsorption processes.
 24. (added) The gas separation and purificationprocess according to any one of claims 2, 3, 5 and 23, wherein moisture,carbon dioxide and other impurity components contained in the raw gasare removed beforehand before the raw gas is subjected to the separationand purification process.